Fault mechanism study on Li‐ion battery at over‐discharge and its diagnosis approach

A detailed research on fault mechanism of lithium (Li)‐ion battery at over‐discharge condition is reported in this study. Cells were cycled with different depths of discharge and reference performance tests were performed to extract parameters in dynamic and equilibrium conditions. The over‐discharge process indicates that the abrupt change of temperature and impedance can be used for fault predication, while the parameter variations from federal urban driving schedule test can clearly identify the fault mode. Curves from incremental capacity analysis suggest loss of active material at negative electrode (LAMNE) as well as Li inventory loss may dominate the over‐discharge process. Finally, post‐mortem examination was carried out to validate authors’ mechanism deduction and diagnosis approach. The proposed approach is suitable for over‐discharge diagnosis and predication in electric vehicle applications.